*another native Russian gurl pops in* She probably means that you've got an linguistic imprecision there. Your translation literally means "I swear (right now) we were infinite (some time ago)". The better version would be "И в тот момент, клянусь, мы были бесконечны". Yours one is kinda hard to understand for natives unu And there's also a comma missed after "клянусь".
Google translator and similar sites kinda mess things up when you try to to use them Synonyms which actually also have tons of translations, hidden idioms, tenses n such, u got the idea. I think there are lots of Russian speakers around (me too! :3) so you would ask them about correct translation. I'm pretty sure that there always are people who would help you and it's always ok to ask, so feel free to do it But your art is really great btw. The palette and style somehow calms me and cheers me up /)UwU(\